Prior to the present invention, lecithin has been included, in only small amounts, as an emulsifier in emulsions for intravenous feeding of patients. Typically these emulsions for intravenous feeding are mediums for intravenously supplying quantities of vegetable oils and fats for nourishment to patients and the amount of lecithin found in these emulsions is generally one percent (1%) or less.
In recent years it has been found that lecithin is not only useful as an emulsifier, but lecithin also possesses valuable physiological properties of its own. Lecithin is involved in various enzyme systems and in the metabolism of lipids, in particular cholesterol because lecithin and other phospholipids have been repeatedly recognized as the natural antagonists of cholesterol in many physical, chemical and biological processes. This is of utmost importance since the human diet contains too often a large excess of cholesterol and saturated fats leading to an accentuated increase of Very Low and Low Density Lipoproteins (VLDL and LDL) in the blood plasma, causing various disturbances particularly atherosclerosis (formation of fatty or "antheromatous" plaques in the intima and media of arteries) and other cardiovascular diseases. As lecithin and other phospholipids, in stimulating the production of High Density Lipoproteins (HDL) in plasma and, thus, compensating whatever increase of VLDL and LDL, do in fact achieve the resolution of atheromatous plaques, it will be desirable to provide an efficient and convenient means for injecting effective amounts of lecithin into the human body to aid in the control of excess cholesterol and fats.
In preparing lecithin for injection into the human body, it is necessary that the injectable preparations containing the lecithin, which may also contain other suitable substances, be physiologically acceptable for injection into the human body. Also, it is desirable that the injectable preparations posses particles with sizes of less than three microns and it is preferable that 95% or more of the particles should measure one micron or less in diameter. Attempts to prepared suitable injectable lecithin preparations have been generally unsuccessful or, at least, unsatisfactory in the past.
Lecithin, for example, is difficult to emulsify in its dry state and does not readily emulsify in water without vigorous shaking and agitation. Furthermore, aqueous dispersions or emulsions of lecithin have limited shelf life and have been found to develop toxic properties after having been stored over a period of time.